Battery Info

[judybug]

Need help choosing correct batteries for my 2004 25' Safari. The batteries already there are one Everstart Marine 500 amps 24ms-6 which I have been able to find at Sears. The other is one 24dp-4 Extreme Deep Cycle Starting battery which I am having trouble finding. I have found a 24dp-4 deep cycle battery also at Sears. Question, is it necessary to have the "extreme" deep cycle or will the 24dp-4 deep cycle provide what is needed? My battery knowledge is that of AAA's and C's. Need help finding soon. Fires in Texas are to close for comfort and can't raise the hitch if it becomes necessary.

[bryanl]

You have two paths to choose between.

One is to follow marketing hype and those in forums who spout their personal anecdotes.

The other is to look at the specifications, cost, and warranty that the manufacturer and retailer will put money on and use those as your guide. Avoid definitions (e.g. 'deep cycle battery' that have no clear meaning supported by pertinent measure)

My suggestion is to get batteries from a reputable retailer who sells a lot to folks like you and will stand behind what he sells. At least use the empirical approach to help you know the costs in your decisions.

The differences between batteries commonly available at retail for RV's are more of degree than kind. You do need to make sure they fit your compartment and have terminals appropriate for your wiring but other than that, its pretty much a commodity market.

Where you will get the most improvement is in your charging and maintenance equipment and how you use your batteries.

Keep in mind that all lead acid batteries have about the same energy density by weight, all of them suffer degradation if subject to deep discharging, they don't like heat, they don't like just sitting (especially when not at full charge),

Take care of your batteries and they'll be there for you when you need to escape.

[Silver Goose]

The marine starting batteries are somewhat of a compromise. Their function is to have enough capacity to start a boat motor, but can provide a prolonged low power drain for lights. In a travel trail application you want a true deep cycle. As previously noted, the specs should be your guide. I would recommend replacing them as matched set.

[judybug]

Thanks for the info. Shopping today will be easier with your quick responses. I love the forum. Thanks

[whitefawn]

My philosophy is to buy the biggest capacity deep cycle battery or batteries that will fit in the compartment. We bought ours at Sears- 115 amp-hours each for capacity, giving us maximum capability for boondocking.

Good Luck-

Joe

[Dakota's Dad]

Make sure you get two batteries that match.. we use 2 interstate series 24 marine deep cycle. About using your jack.. plug in. Use a regular extension cord if needed, and your 20amp adapter.. you only need to run that one thing, not the A/C to get it hooked up... or plug into your TV.. it's battery/alternator will power your jack.

[bryanl]

re: "The marine starting batteries are somewhat of a compromise."

This is an example of what I mean when I suggest being careful with marketing terms and things that don't have clear objective meanings supported by proper and pertinent measure.

All batteries are a compromise. With lead acid batteries, the main trade-offs are cost, capacity, and ruggedness. You can see this if you look at a manufacturer's line card. You will also see that the variances are really not that significant, especially when compared to inherent variabilities in batteries in use.

Terms like "deep cycle" and "marine/RV" are labels put on batteries to indicate their target market and qualify the warranty. They have no clear definition of just what they mean in terms of battery performance that can be measured (else why not just spout the measure?).

[Mexray]

As mentioned above, the 'Deep cycle/Starting' label is just a marketing effort...

All Deep Cycle batteries will provide enough energy to 'start' engines, within the battery's rated capacity...

The higher Cold Cranking Amp ratings of true starting batteries are a result of greater battery plate 'area', as starting batteries have 'thinner' plates so more can be installed in a given battery case size - More plate 'area'...

Deep Cycle batteries have 'thicker' plates which would limit the number of plates that could be installed in a given battery case...

Therefore, a Deep Cycle battery of the same case size as a 'starting' battery will have a lower Cold Cranking Amp rating - but will still provide enough energy to operate many 'starting' applications...

Don't be fooled with ratings such as 'MCA' - Marine Cranking Amps, which is available cranking amps at 32 degrees f, as is ALWAYS higher than 'CCA' Cold Cranking Amps which is the rating at 0 degrees f...

MCA or RVCA was 'invented' by marketing types to make a battery 'appear' to have a higher performance, when it's actually uses different data - batteries always perform better as they warm up in temp...

You actually need to look at AH's - Amp Hour ratings when looking for you AS's 'house' batteries...

Get two matching Deep Cycle batteries - probably Group-24's - look for the highest AMP HOUR rating you can find - probably about 80 AH for the better quality batteries...

[bryanl]

re: "Deep Cycle batteries have 'thicker' plates"

as far as batteries commonly available for us RV types, this isn't the case. They are all about a tenth of an inch thick, plus or minus half that (re NAWS), and a paste in a grid construction. Plate strength these days is more a matter of alloy than mechanics.

The first problem, though, is finding some useful definition for "deep cycle battery" that is pertinent to our needs and shows in some measurable way. If you find such a definition and measure, please let me know as I have been looking for a long time. All I have found to date is that the term identifies a target market and qualifies the warranty somewhat.

[Hibby]

I am looking at new batteries as well. I am considering Optima D34M because they will fit in the cases that I currently have, and because I have a person in my office whose husband works for Optima and can get them for me at a substantial discount.

Is it more important to consider the "reserve capacity" (120) or the "C/20 capacity" (55) for these batteries, and is there a better choice?

[Mexray]

Hibby....

Optima's are good for their intended purpose, but their limited AMP HOUR capacity (55 AH's) compared with Group-24 flooded cell or AGM type batteries (about 80 AHs) limits the amount of energy you'll have available when you're not hooked up to shore power...

In other words, you're giving away about 30% capacity (each) when using the 55 AH Optimas, as compared with rectangular Group-24 flooded cell batteries...

If you rarely camp WITHOUT shore power hookup, then it really isn't an issue, the Optimas would be OK...

[Hibby]

Okay, that's good to know! I'm so appreciative of the forums for what I am able to learn before making mistakes!

Thanks, Mexray!

[Castaway]

Interesting and timely post. I too am looking for a battery to run my Coleman Travel Cooler, manual says it draws 4 AMPS. I would like a battery that will run the cooler for about 20 hrs, is that possible? If so what should I look for in battery specs ie: How many AMP Hrs ?


Gary

[bryanl]

4 amps, 20 hours, that's 80 amp hours. theoretically.

Generally, you'd only want to use 50% of your battery's capacity on a regular basis so that means 160 AH of battery.

Then you'd need to add in a bit to cover available energy variability due to temperature, age, cycle to cycle variation and so on - add another 20% or so for this and that gets it close to 200 AH.

Then you'd want to include some reserve capability. That generally means another 50% to 100% to bring the requirement up to 300 AH or more.

Now you need to figure a good 12 hour recharge time (if you have the proper equipment). If that is going to eat into your planned usage cycle, you'll need to accommodate that somehow.

Yes, you could get by with a typical group 27 battery but you'd have no reserve and you'd be using it hard. For cost effective utilization with a reasonable reserve, you'd need 3 of those batteries if the need was a routine thing. ... this is the sort of analysis that indicates why this particular cooling system is not in wide use (not to mention that, if it is a peltier device, it is really rather inefficient).

also note that most batteries include a 20 hour energy capacity rate. For a group 27 battery, that means about a 60 watt load. Your cooler uses a bit less power than this which means that you could expect a bit more available capacity from the battery. (research Peukert on this).